Computer data communication networks are used to transmit information between geographically dispersed computers and between user devices such as computer terminals or workstations and host computer applications. A variety of communication architectures exist. Two such data communication architectures are the IBM System Network Architecture (SNA) and the International Standards Organization's (ISO) Open System Interconnection (OSI) architecture. One embodiment of IBM's System Network Architecture is described in a co-pending, commonly assigned United States patent application, Ser. No. 08/245,053, entitled "Virtual Route Resynchronization", the entirety of which is hereby incorporated herein by reference.
High Performance Routing (HPR) is a recent enhancement to the IBM Systems Network Architecture. HPR uses rapid transport protocol (RTP), and the logical connection between two HPR-capable nodes is called an RTP connection. The ends of the connection are referred to as the RTP endpoints, while any intermediate nodes along the RTP connection route are called the automatic network routing (ANR) nodes. Error recovery on an RTP connection is done end-to-end rather than node-to-node, meaning that only the RTP endpoints are involved.
Many end-user sessions can flow on a given RTP connection. Also, data messages sent on an RTP connection can get lost in the network or might arrive out of order at the destination RTP endpoint. Each message that flows on an RTP connection is assigned a byte sequence number (BSN) which enables the destination node to determine when data is lost or arrives out of order. It is critical that the origin RTP endpoint fill in the correct BSN when sending out a message, otherwise the RTP connection will fail causing all the end-user sessions to also fail.
Because of the need to maintain the sequence of messages between the data host and other components, communications with a failing unit can only be restarted if the sequence number information is known or if the entire communications network is reinitialized. Reinitialization of a large network is highly undesirable because of the considerable time required. This lost time can be costly to a business that is dependent upon transaction processing for its operations. Various schemes have been proposed for retaining sequence information so that the network can be restarted without reinitialization. However, data host failure may occur unpredictably and may not afford an opportunity to save the necessary sequencing information. In these situations, a network reinitialization is required. There is therefore a need to have a system or method for resynchronizing data communications without reinitializing the network.
The present invention addresses the technical problems of recovering synchronization information lost during a network component failure. It is also directed to the problem of resynchronizing message traffic between adjacent communication components following a component failure.